Organothiophosphate insecticides are well known and widely used for crop protection. Included among these are Counter (terbufos), Thimet (phorate), Mocap (ethoprop), Torak (dialifor), Trithion (carbophenothion), Nialate (ethion), Navadel (dioxathion), Dyfonate (fonofos), and Imidan (phosmet).
An unfortunate aspect of many of these compounds is a mercaptan odor. The presence of mercaptans in compositions or formulations of these compounds is due to a number of factors. In some cases, the mercaptans serve as starting materials for the synthesis of these compounds, and their presence in the final product is the result of trace amounts of unreacted starting material. These compounds also tend to degrade or decompose to produce mercaptans, particularly when subjected to heating or conditions promoting acid hydrolysis. Still further, thiophosphite analogs of the compounds are present in some cases as by-products of the synthesis, and these thiophosphite species have a high tendency to decompose to mercaptans. Regardless of the mechanism by which the mercaptan odor is produced, it is undesirable from an environmental point of view as well as for handling and field application purposes.